Metal article and method of production



March 12, 1940. F. c. ELDER 2,192,901

METAL ARTICLE AND METHOD 0F PRODUCTION Filed Feb'. 18. 1939 @wh/W Patented Mar. 11.251940 UNITED STATES PATENT wOFFICE METAL ARTICLE AND METHOD OF PRODUCTIDN This invention relates to wires and the like,

either individually or stranded, particularly to coated wires or strands that are adapted for use as electrical transmission lines, guy or stay wires, messenger wires, etc. herein, is intended to embrace all elongated metal bodies, of whatever cross-sectional shape, that are relatively exible.

Wires to be used as overhead transmission lines f are required to possess certain physical properties of electrical conductivity, tensile strength, and resistance to. corrosion, in order to comply with commercial specifications. Commercial specifications provide for several diiierent grades 5 of wires or strands of this type iii-recognition of the fact that certain physical properties required for certain uses differ from those required for other uses, and that no single wire capable of providing the optimum as to one class of physical properties is capable of manifesting the optimum of physical properties of another class.

More specifically, it is recognized that the factors entering into the manufacture of a Wire, best g5 adapted from the standpoint of electrical con-n ductivity, are not those which are conducive for the imparting of the best tensile characteristics,

and vice-versa. For this reason, different corn-a mercial grades have been established to specify 04 electrical conductors of the type required. The most common of these are three: E. B. B., B. B., and Steel. Where the electrical properties are non-essential or are secondary to high strength characteristics, a separate classification based on |5 tensile properties is recognized, four in number: Common, Siemens-Martin, High-Strength, and Extra High Strength. In all of these grades the higherA the tensile strength the poorer are the electrical properties, and vice-versa; the E. B. B.

,0 grade representing wires of the best electrical properties and of the lowest mechanical strength, and the Extra High Strength grade representing wires having the poorest electrical properties and the greatest mechanical strength.

,5 It has, heretofore, not been considered possible to combinethe best features of these several grades of wires in one, unitary conductor, since, as has been mentioned above, the factors entering into the manufacture of each, which will be o discussed in full hereinafter, are such as to detract from certain of the physical properties, While enhancing some of the others.

Another very important factor,.in considering wiresof the type in question, is that of resistance 5 to corrosion, which is usually provided for by the The term wire, as used addition of a protective coating, such as zinc, upon the surface of the wire. The coating, in addition to being initially impervious to corrosive inuences, must be capable of remaining impervious; as, by being resistaint to cracking when 5 the Wire is bent and flexed; and of a certain weight, prescribed by commercial standards, which will insure that the wire will be protected against corrosion for a'predetermined period of time. Many of the physical properties entering 30 into the acquisition of a good impervious coating, which will withstand flexing and other con ditions of service without failing, are directly re lated to the physical properties contributing to the strength and electrical properties of the conit ductor, per se, and it is Well established that those properties conducive to the acquisition of the best coating are not always provident of the best electrical and mechanical characteristics.

It is an object of the present invention to prc- @a vide a wire of the class described which has electrical characteristics closely resembling those of the E. B. B. grade of conductors, while, at the same time, manifesting tensile strength charac teristics comparable to those of the High Strength gg grade of wires.

It is another object to provide such a conductor with a corrosion resistant coating that is adherent, and, in weight and physical characteristics, that is as satisfactory from I the commercial 30 speciiication standpoint as the coatings 'to be found on any of the conductors or wires of the grades aforementioned.

It is still another object to provide a high tensile strength wire, low in carbon and other cie 35 mental inclusions, or, if relatively high in any of the latter, then, of greater tensile strength for the amount included than other Wires of corresponding analysis, Which has a hot-dipped coating of corrosion resisting metal firmly bonded 40 thereto, and of an amplitude equal to or greater than coatings on corresponding Wires of the same commercial class.

It is a further object to provide a wire of the class described whose tensile properties, electrical e5 conductivity, and corrosion resistant coating Vwill be of an higher order relative to the carbon, manganese, and other elemental inclusions, than any other wire ci similar analysis of the corresprmdfs ing commercial class. Si@

Other objects and advantages will become ap" parent hereinafter? after consideration is given to the specification wherein certain preferredeinu bodiments oi my invention are set forth.

The present invention, constitutes partial con g5 thereof, are developed by the inclusion of certain elements therein in relatively high amounts; for instance, carbon and/or manganese, present in such amounts as to characterize the steel as a high carbon or high metalloid steel impart relatively high tensile values thereto. The manganese inclusions,'ineffectual in and of themselves without the presence of carbon, serve to enhance or augment the functions of the latter in raising the tensile properties of the steel; particularly, when a quench is employed after the carbon-manganese steel has been subjected to heat-treatment.

Another way to develop the tensile properties of steel, either complementary or supplementary to the chemical inclusions therein, is by working the metal at certain temperatures, and, particularly, by the so-called cold-working.

It is also well known that the inclusion of such elements as carbon and manganese, for the development of the tensile properties of'steel, is accompanied by an increase in resistance to the passage of electrical current through the steel in a fairly direct proportion to the amounts added. Furthermore, the quench sometimes employed to develop the ultimate in tensile properties of such steels is known further to impair the electrical properties thereof. It is for these reasons that high strength steels are usually relatively poor conductors of electricity, and the low strength steels are the best conductors thereof.

It has also hitherto been known that the presence of certain elements, such as carbon, silicon, etc., in the metal to be coated, is conducive to the acquisition of a good hot-dipped coating of zinc, but here, again, the presence of such elements in any amount to be effective from a coating standpoint, is harmful .to the electrical properties in that the elements increase the inherent resistance of the steel to the passage of electrical current. On the other hand, cold-working is known to benefit the coating by augmenting its bond with the base metal, and by improving the physical characteristics of the coating, so that it is better able to withstand iiexing, and other strains and stresses encountered in service, without failing. Thus, a coating on low metalloid stock, which might otherwise be unsatisfactory, is rendered satisfactory by substantial coldreduction.

I have discovered that a steel low in metalloids, which is the best from the standpoint of electrical properties, may be endowed with great tensile strength by cold-working after it has been subjected to all treatment wherein it encounters heat in any substantial amount; as, for instance, in hot-galvanizing baths, annealing'operations', etc. Such a steel, to meet the corrosion resistance requirements of the trade, must be galvanized, which presupposes that the metal, if hot-galvanized, is subjected to the coating operation before cold-working to final size; or, else, that the coating operation is one that does not involve the application of substantial temperature to the base metal; as, for instance, by electro-deposition. 'Ihe present invention is principally concerned with the application of the ycorrosion resisting coating to the base metal by the hot-dip method, which, in accordance with the teachings of theinventiommust be accomplished before the reduction to nal size is undertaken. Cold-working a metal body after it has been coated, as by drawing hot-galvanized wire, effects a reduction in the thickness of the coating at any given point on the surface of the metal,

so that, if the end product is to have a sufilcient thickness of coating to meet the commercial requirements, an extremely heavy coating must be initially provided before the drawing operation is commenced.

Until the advent of the issuance of my U. S. Letters Patent No. 2,049,834, pertaining to methods of coating, there was no way known to the trade of applying a sufficiently heavy coating by the hot-dip method, which coating could be subjected to the substantial reductions required to raise the tensile strength of the base metal, and still remain of suiiicient amplitude per unit area of coated surface, after the drafting operation, to meet the commercial standards and trade specifications. Electro-deposition methods presented the only-possible alternativeby which this could be done, but, by virtue of the relatively slow and expensive nature of this process, it is rendered wholly impracticable from a commercial standpoint, and, so far as is known, has never been undertaken by anyone.

r I he single gure of the drawing is a. side elevation with part shown in section of an apparatus suitable for practicing the improved method and making the improved product.

Referring briefly to the apparatus, B represents a zinc pan such as shown in my above identified Letters Patent, and which is provided with a burner 'I at an entrance end which malntains the zinc bath molten. 'I'he material A topulled through the apparatus by a suitable pullv ing block or take-up reel I5.

One preferred manner of carrying out my invention is by providing a steel v,rod or wire of low metalloid content; that is, low in carbon, manganese, and other elements which are usually employed to improve physical properties method; one suitable mode for effecting the latf ter being disclosed and described in my prior patent, referred to above.

The over-size rod or wire coated in this manner is then subjected to cold-working. as by being drawn through reducing dies, until the required size is attained. Providing the reduction is substantial, as whensomething in excess of 60% reduction in cross-sectional area is had, the tensile properties of the material will be found to have been materially raised anywhere from 2 to 5 times their original values depending upon the extent of the reduction and the composition of the material. The drafting practice will have been responsible for the establishment of a rm bond between the coating metal` and the base metal as well as for the material improvement of the physical properties'of the coating metal. By virtue of theheavy coating initially put on, the wire after drafting will still retain a suilciently heavy coating to meet theI commercial specifications. ,As a specific example of the present invention, a inch diameter rod of the following analysis; carbon .05%, manganese .10%, phosphorus .005% sulphur 023%, silicon 005%, and the balance substantially pure iron, was reduced to .192 inch diameter, representing a 74% reduction. This wire was then galvanized in hot zinc without annealing (other than that attendant upon being immersed in the molten zinc). order of flve ounces per square foot' of zinc Was applied representing a thickness of coating metal in the order of .015, thus increasing the over-all size of the wire from .192" to .207". The wire thus coated was then drawn to .072" over-all diameter, representing a total reduction of about 88%. This wire had a tensile strength of 135,000 pounds per square inch; an A. C. resistance of 5090 mile-ohm-pounds, yielding a skin eiect A. C.D. C. ratio of 1.165. Such values, as compared with the tensile strength of this magnitude, have heretofore not been obtained in wires of any known kind.

The following table shows how a wire prepared in accordance with the present invention (No. 12) compares with other wires of the samel fin- A coating in the ci coating, expressed in ounces a square foot, as prescribed by the American Society for Testing Materials, are given below, with respect to the size of the wire, expressed in fractions of an inch diameter:

ASTM specifications (Anz-23) for galvanized wire `strand (Wetight xf coating ex ra ga van ze Slze of wire inches diameter ounces/Square surface Coatings lighter than these are not acceptable, vfor the sizes given, insofar as standard extra or double galvanized coatings are concerned. From this, it may be computed what the initial amount of coating must be to permit cold reduction to finished size after coating, still to maintain the requisite weight of coating metal. The extent of ished size made in accordance with standard reduction permitted for any given weight of coatcommercial practices now in vogue. ing is determined by the application of the follow- Type of steel A (hrcslst' D. C. resistivity v Chemical analysis Finish Size Lbs. Tenqne Skin effect Treatment dimm per stre'gth A. C.p. C. Grade M qu inch mile- Mile Ohms M1 h 0121315' who 8D- i 1 per 1 e 0 m, Carbon ganese con gigi 1,000 lbs. m@1e 40 feet 68o F Per cent Per cent 1 BB 15 max. .109 167.3 57, 500 8, 807 9. 97 5. 609 33. 52S 1. 570 2. 425 10U 167. 3 ,000 8, 860 10. 03 7, 535 45. 038 1.175 3, .612 .100H 167.3 199,000 9,408 10.65 8,833y 52.80 1.065 410 210 .010 Hot galvanized 109 107.3 000 5, 300

after annealing. .410 .210 .010 Heat treated- .109 167.3 135,000 5,400

drawn-then hot i galvanized. .350 .20 .l0 Hot galvanized 109 167 3 72,500 6,000

after annealing. .350 .20 .l0 Hot galvanized .100 167 3 120,000 6,070

iwlthnut anneclng. 210 .109 167. 3 125, 000 7, 800 8. 83 5, 610 25-. 60 109 167. 3 59, 000 9, 630 11. 0 6, 500 39 1 48 25. 60 10615 160 59, 000 8, 760 10. 4'- 5, 580 35 1 57 20 110 167. 4 49, 500 8, 720 9. 88 4. 980 30 1. 75 im 12. Present iI1- 03-. 04 12-. 15 Galvanized hard 109 167. 3 138, 000 7, 250 8. 21 4, 767-4, 899 20. 3 1. 48

vention. and drawn after. Av.=4, 833

From the foregoing table, it will be seen that I have provided a wire having tensile characteristic comparable to those of a high strength grade of wire, but which has electrical properties better than those specified for the E. B. B. grade 0f Wire. 1n addition, the coating corresponds in thickness to that which is commercially known as an extra or double galvanized coating, for^ the nished size of wire in question (.109), which in weight, is .8 or more ounce per square foot of wire surface. Such a coating possesses the requisite physical values to permit its being flexed and bent Without cracking, and is especially `Well bonded to the base metal, by virtue of the drafting to which it has been subjected. i

For the class of wires in question, i. e., electric transmission lines and high strength guy or stay wires, the commercial standards for the weights ing table, which represents data of empirical approximations, relative to the diminution of coating, expressed in ounces a square foot per percentage of reduction in cross-sectional area:

Weight of coating Per cent1-reduction cross-sectional area in ouificesquare Initial coating nine percent (59%) reduction, which would be less than double its original tensile value. Ordinary high metalloid steel, (C=0.80%), would not be increased in tensile strength more than 60,000 pounds per square inch by such a reduction, representing an increase of less than double its original tensile value.

As the comparative table, listed above, shows, the steels similar to example No. l2 have tensile values appreciably more than double the original values of steels having carbon and manganese contents within the ranges given, since such steels usually start with a tensile value around 40,000 pounds per square inch as a maximum. Carbon steels, on the other hand, in which the carbon content approximates 0.80%, start with a tensile value of about 100,000 pounds per square inch. The low metalloid stocks will increase in tensile strength at the rate of about 550 munds per square inch for every one percent (1%) reduction in cross-sectional area, while the carbon steel, suggested above, will increase about 1,000 pounds per square inch for every one percent (1%) reduction.

Thus, it will be seen 59 percent reduction is not suillcient to elevate the tensile strengths of these steels up to the desired values. Unless a heavier initial coating is provided, the tensile values must be limited to those procurable by such reduction. In accordance with the present invention, by starting with a heavy coating, such as was not possible of achievement by any hot-dlp methods known to the trade prior to the issuance of my patent, above identified, I may carry the draughting practice to any point of reduction short of 100%, and nish with the weight of coating specied as standard for such nishing size, while enjoying an elevation of tensile strength that-is not dependent upon elemental inclusions in the steel that adversely eect its electrical properties, nor dependent upon such processing, as quenching after heat treatment, from which impairment of the electrical properties likewise results.

coated wire cold Worked subsequent to coating to produce a wire whose physical properties have a ratio of tensile strength, as expressed in pounds per squareinch to its electrical resistivity, as expressed in pounds per mile ohm, higher than 25 to 1 with the actual direct current resistivity under 5,000 Apounds per mile ohm and with the nished coating of an amplitude corresponding to that which is known as extra or double galvanized coating.

2. A ferrous metal wire having a carbon content of .25 percent or less and a manganese content equal to or less than the carbon content, a heavy galvanized coating alloyed thereto, said coated wire cold worked at least 59% subsequent to coating to produce a wire Whose physical properties have a tensile strength of at least 125,000 pounds per square inch and with an actual direct current resistivity under 5,000 pounds per mile ohm and the nished coating being of an amplitude corresponding to that which is known as extra or double galvanized.

FLINT C. ELDER. 

